FIG. 1 is an illustration of a network 100 and devices 110, 112, 114, 116, 118 and 120 connected to the network 100 by way of one or more wired or wireless links. The devices depicted in FIG. 1 are distributed spatially according to their current geographic locations. Typical wireless carriers can use various approaches for determining the current geographic location of a device. One high accuracy approach actives a Global Positioning System (GPS) receiver in a mobile device in order to develop a reasonably precise location of the mobile device at a point in time. A low accuracy approach maps the cellular tower that a mobile device is communicating with (e.g., based on signal strength) to a geographic region. An intermediate approach uses one or more last known GPS location(s) to determine a location of the mobile device based on an estimated trajectory. Other approaches are possible.
The network 100 can include tethered devices (120) such as personal computers, base stations (104, 106, 108) for providing wireless network service to mobile devices (110, 112, 114, 116, 118) such as cellular telephones, mobile computers, portable game systems, portable media devices, personal and automobile navigation systems (116), combinations of these, and generally any type of mobile computing device that is capable of communicating wirelessly. Examples of wireless networks include cellular telephone networks, Institute of Electrical and Electronics Engineers (IEEE) 802.11 based networks, IEEE 802.16 based networks, and other suitable networks. The network 100 can include one or more servers 102 for facilitating different network functions such as switching packets between devices or base stations, coordinating mobile device handoff in cellular networks, and supporting applications such as Short Message Service (SMS), Short Message Service Center (SMSC), Instant Messaging (IM), Multimedia Message Service (MMS), video phone, and email.
Users of mobile and tethered devices can exchange messages with one another. For example, if a user of the mobile device 114 wants to send a message to friends that are using mobile devices 110 and 118, the user can specify the destination addresses associated with these devices (e.g., the friends' email account names) in a message sending application, such as electronic mail (email) or an IM application. Once the message is sent, the message is received by base station 108, transmitted by base station 108 to server 102, and relayed from server 102 to base stations 104 and 106. Base station 106 transmits the message to mobile device 118 and base station 104 transmits the message to mobile device 110.
If the user of mobile device 114 also wants to communicate their current location, the user can manually include this information in the message: “Meet me at the pub at Powel and Market in 15 minutes.” However, having to type the location information can be cumbersome, especially using the minuscule keypads that are commonly included on mobile devices such as cellular telephones. In addition, the user may have no idea of where the user's friends are currently located, or whether they can actually arrive at the user's location within the specified time. The user may want to send a message just to friends who are within a certain distance from the user's current location, but the user has no way of knowing which friends are nearby.